// Set the producer group name.
DefaultMQProducer producer(groupName);
// Set the service access address.
producer.setNamesrvAddr(nameserver);
// Set user permissions.
producer.setSessionCredentials(
    accessKey,  // Role token.
    secretKey, // Role name.
    "");
// Set the namespace (full name of the namespace).
producer.setNameSpace(namespace);
// Ensure that all parameters are set before startup.
producer.start();

// Initialize the message content.
   MQMessage msg(
       topicName,  // Topic name.
       TAGS,        // Message tag.
       KEYS,        // Message business key.
       "Hello cpp client, this is a message."  // Message content.
   );
   
   try {
       // Send messages.
       SendResult sendResult = producer.send(msg);
       std::cout << "SendResult:" << sendResult.getSendStatus() << ", Message ID: " << sendResult.getMsgId()
           << std::endl;
   } catch (MQException e) {
       std::cout << "ErrorCode: " << e.GetError() << " Exception:" << e.what() << std::endl;
   }

// Release resources.
   producer.shutdown();

// Message listening.
   class ExampleMessageListener : public MessageListenerConcurrently {
   public:
       ConsumeStatus consumeMessage(const std::vector<MQMessageExt> &msgs) {
           for (auto item = msgs.begin(); item != msgs.end(); item++) {
               // Business.
               std::cout << "Received Message Topic:" << item->getTopic() << ", MsgId:" << item->getMsgId() << ", TAGS:"
                         << item->getTags() << ", KEYS:" << item->getKeys() << ", Body:" << item->getBody() << std::endl;
           }
           // If consumption is successful, return CONSUME_SUCCESS.
           return CONSUME_SUCCESS;
           // If consumption fails, return RECONSUME_LATER. The message will be consumed again.
           // return RECONSUME_LATER;
       }
   };
   
   // Initialize the consumer.
   DefaultMQPushConsumer *consumer = new DefaultMQPushConsumer(groupName);
   // Set the service address.
   consumer->setNamesrvAddr(nameserver);
   // Set user permissions.
   consumer->setSessionCredentials(
       accessKey,
       secretKey, 
       "");
   // Set the namespace.
   consumer->setNameSpace(namespace);
   // Set the instance name.
   consumer->setInstanceName("CppClient");
   
   // Register a custom listener function to handle received messages and return the processing result.
   ExampleMessageListener *messageListener = new ExampleMessageListener();
   // Subscribe to messages.
   consumer->subscribe(topicName, TAGS);
   // Set the message listener.
   consumer->registerMessageListener(messageListener);
   
   // After completing the preparations, you must call the startup function for the system to function properly.
   consumer->start();

// Release resources.
consumer->shutdown();

        MQMessage msg("console topic", "tag", "Delay Message.");
        chrono::system_clock::duration d = chrono::system_clock::now().time_since_epoch();
        chrono::milliseconds mil = chrono::duration_cast<chrono::milliseconds>(d);
        // Scheduled delayed message, in milliseconds, indicating that messages are delivered at the specified timestamp (after the current time).
        // Set the time for delayed or scheduled delivery, for example, delivered 30 seconds after the current time.
        long expectTime = mil.count() + 30000;
        msg.setProperty("__STARTDELIVERTIME", to_string(expectTime));